Strain Engineering of Photo-induced Topological Phases in 2D Ferromagnets

We argue that strain engineering is a powerful tool which may facilitate the experimental realization and control of topological phases in laser-driven 2D ferromagnetic systems. To this extent, we show that by applying a circularly polarized laser field to a 2D honeycomb ferromagnet which is uniaxially strained in either the zig-zag or armchair direction, it is possible to generate a synthetic Dzyaloshinskii-Moriya interaction (DMI) tunable by the intensity of the applied electric field, as well as by the magnitude of applied strain. Such deformations enable transitions to phases with opposite sign of Chern number, or to trivial phases. These are basic results that could pave the way for the development of a new field of Strain Engineered Topological Spintronics (SETS).Comment: 11 pages; enlarged version relatively to version V

Two-level systems coupled to Graphene plasmons: a Lindblad equation approach

In this paper, we review the theory of open quantum systems and macroscopic quantum electrodynamics, providing a self-contained account of many aspects of these two theories. The former is presented in the context of a qubit coupled to a electromagnetic thermal bath, the latter is presented in the context of a quantization scheme for surface-plasmon polaritons (SPPs) in graphene based on Langevin noise currents. This includes a calculation of the dyadic Green’s function (in the electrostatic limit) for a Graphene sheet between two semi-infinite linear dielectric media, and its subsequent application to the construction of SPP creation and annihilation operators. We then bring the two fields together and discuss the entanglement of two qubits in the vicinity of a graphene sheet which supports SPPs. The two qubits communicate with each other via the emission and absorption of SPPs. We find that a Schrödinger cat state involving the two qubits can be partially protected from decoherence by taking advantage of the dissipative dynamics in graphene. A comparison is also drawn between the dynamics at zero temperature, obtained via Schrödinger’s equation, and at finite temperature, obtained using the Lindblad equation

The polarizability of a confined atomic system: an application of the Dalgarno-Lewis method

In this paper we give an application of the Dalgarno–Lewis method, the latter not usually taught in quantum mechanics courses. This is very unfortunate since this method allows one to bypass the sum over states appearing in the usual perturbation theory. In this context, and as an example, we study the effect of an external field, both static and frequency-dependent, on a model atom at fixed distance from a substrate. This can happen, for instance, when some organic molecule binds from one side to the substrate and from the other side to an atom or any other polarizable system. We model the polarizable atom by a short range potential, a Dirac-δ, and find that the existence of a bound state depends on the ratio of the effective 'nuclear charge' to the distance of the atom from the substrate. Using an asymptotic analysis, previously developed in the context of a single δ-function potential in an infinite medium, we determine the ionization rate and the Stark shift of our system. Using Dalgarno–Lewis theory we find an exact expression for the static and dynamic polarizabilities of our system valid to all distances. We show that the polarizability is extremely sensitive to the distance from the substrate, creating the possibility of using this quantity as a nanometric ruler. Furthermore, the line shape of the dynamic polarizability is also extremely sensitive to the distance from the substrate, thus providing another route to measure nanometric distances. The didactic value of the δ-function potential is widely accepted in teaching activities due to its simplicity, while still keeping the essential ingredients of a given problem.The authors acknowledge João Carlos Henriques and Thomas G Pedersen for many discussions and exchanges of ideas on this topic. NMRP acknowledges support from the European Commission through the project 'Graphene-Driven Revolutions in ICT and Beyond' (Ref. No. 785219), and the Portuguese Foundation for Science and Technology (FCT) in the framework of Strategic Financing UID/FIS/04650/2019. In addition, he acknowledges COMPETE2020, PORTUGAL2020, FEDER and the Portuguese FCT through Projects POCI-01-0145-FEDER-028114, POCI-01-0145-FEDER-029265, PTDC/NAN-OPT/29265/2017, and POCI-01-0145-FEDER-02888. TVCA acknowledges the FCT for a grant given in the context of the 'Quantum Matter|Materials and Concepts Summer Training Program 2020'

Upper and lower bounds for the bearing capacity of foundations on soft soils with reinforcement columns

The finite element program mechpy, developed within the authors’ team, which implements the upper and lower bound theorems of limit analysis, is applied to the calculation of the bearing capacity of foundations on soft soils improved with reinforcement columns. The problem is analysed in two and threedimensions, considering the soil and the columns responding under undrained conditions, using different replacement area ratios and different column-to-soil shear strength ratios. The upper and lower bound results are found to be in a narrow range and in good agreement with experimental results found in the literature. A simple equation is proposed to evaluate the bearing capacity of soil reinforced with columns.publishersversionpublishe

Utilização de revestimentos à base de alginato na conservação pós-colheita de manga Tommy Atkins.

O objetivo deste estudo foi avaliar a qualidade de mangas Tommy Atkins após a aplicação de revestimentos ‡ base de alginato e mantidas sob armazenamento refrigerado seguido de temperatura ambiente

Infections with Avian Pathogenic and Fecal Escherichia coli Strains Display Similar Lung Histopathology and Macrophage Apoptosis

The purpose of this study was to compare histopathological changes in the lungs of chickens infected with avian pathogenic (APEC) and avian fecal (Afecal) Escherichia coli strains, and to analyze how the interaction of the bacteria with avian macrophages relates to the outcome of the infection. Chickens were infected intratracheally with three APEC strains, MT78, IMT5155, and UEL17, and one non-pathogenic Afecal strain, IMT5104. The pathogenicity of the strains was assessed by isolating bacteria from lungs, kidneys, and spleens at 24 h post-infection (p.i.). Lungs were examined for histopathological changes at 12, 18, and 24 h p.i. Serial lung sections were stained with hematoxylin and eosin (HE), terminal deoxynucleotidyl dUTP nick end labeling (TUNEL) for detection of apoptotic cells, and an anti-O2 antibody for detection of MT78 and IMT5155. UEL17 and IMT5104 did not cause systemic infections and the extents of lung colonization were two orders of magnitude lower than for the septicemic strains MT78 and IMT5155, yet all four strains caused the same extent of inflammation in the lungs. The inflammation was localized; there were some congested areas next to unaffected areas. Only the inflamed regions became labeled with anti-O2 antibody. TUNEL labeling revealed the presence of apoptotic cells at 12 h p.i in the inflamed regions only, and before any necrotic foci could be seen. The TUNEL-positive cells were very likely dying heterophils, as evidenced by the purulent inflammation. Some of the dying cells observed in avian lungs in situ may also be macrophages, since all four avian E. coli induced caspase 3/7 activation in monolayers of HD11 avian macrophages. In summary, both pathogenic and non-pathogenic fecal strains of avian E. coli produce focal infections in the avian lung, and these are accompanied by inflammation and cell death in the infected areas

Qualidade e conservação pós-colheita de cebola ‘Vale Ouro’ submetida a doses de nitrogênio e potássio em cultivo convencional, no Submédio do Vale São Francisco.

Suplemento. Edição dos Trabalhos do 49 Congresso Brasileiro de Olericultura, Águas de Lindóia, ago. 2009

Conservação pós-colheita de cebola ‘Brisa’ sob influência de doses de nitrogênio e potássio, no Submédio do Vale do São Francisco.

Suplemento. Edição dos Trabalhos do 49 Congresso Brasileiro de Olericultura, Águas de Lindóia, ago. 2009

Caracterização física e química de maracujá-do-mato (Passiflora cincinnata Mast.) colhido em dois estádios de maturação.

Este trabalho teve como objetivo a caracterização física e química do maracuja-do-mato (Passiflora cincinnata Mast.) colhido em dois estádios de maturação